1. Field of the Invention
The present invention relates in general to reciprocating engine pistons and pertains, more particularly, to a system for sealing the gap between the piston and cylinder walls of such an engine. Even more particularly, the invention relates to a piston sealing system incorporating gas bearings to reduce friction and to achieve low fluid leakage between the piston and the engine cylinder wall.
2. Background Discussion
The means for sealing the gap between a piston and the cylindrical walls of a reciprocating engine generally consists of a set of piston rings lubricated by oil. With such an arrangement, both the piston and walls are maintained at a temperature sufficiently low that the desired lubricant properties are maintained. As a result, the low wall temperature, relative to the temperature of the gas working fluid contained in the engine chamber, leads to a significant loss of heat from the engine working fluid by heat transfer to the cooled piston and cylinder walls that significantly reduces the efficiency of energy conversion, by the engine combustion of fuel, to mechanical work.
Accordingly, a general objective of the present invention is to achieve a higher engine efficiency through the preferred elimination of oil lubricant and the use of engine working fluid to achieve the required piston seal function of preventing significant leakage of gas from the engine chamber past the piston while maintaining low resistance by the engine cylinder walls to the reciprocating movement of the piston.
With respect to known prior art, reference is now made herein to U.S. Pat. No. 2,884,282 to Sixsmith, as well as U.S. Pat. Nos. 4,413,864 and 4,496,194 to Phillips. In this connection, it is noted that a gas bearing comprised of a cavity on one of two interfacing surfaces, wherein a means is provided for gas, or air, to flow from a source to the cavity, and from there leak past the small gap around the edge of the cavity to in between the two interfacing surfaces, is well known. The Sixsmith patent illustrates the manner in which three such air bearings are applied to support a rotating solid cylindrical shaft.
In the Phillips patents there is described a gas bearing applied to a planer surface wherein one of the interfacing bodies contains a cavity into which air is supplied.